Application fields of dielectric barrier discharge lamps which are of importance at present are those of office automation, in particular linear lamps for scanners, fax machines and similar appliances and large-area, flat lamps, so-called flat radiators, for backlighting monitors and television screens using liquid crystal technology and other graphical displays. However, the invention is not restricted to these application areas. Instead, further application areas exist, for example in UV treatment in trade and industry, in general lighting, in luminaire design etc.
Dielectric barrier discharge lamps are known, when considered per se, and have been extensively documented in the meantime in the prior art. They are characterized by the fact that the electrodes are separated from the discharge medium located in the interior of the discharge vessel by a dielectric. In this case, in principle the electrodes can either be arranged with them all on the inside, all on the outside or with the electrode(s) of one polarity on the inside and the other(s) on the outside of the discharge vessel. For electrodes arranged on the outside of the discharge vessel, the wall of the discharge vessel acts as a dielectric barrier. If all of the electrodes are arranged inside the discharge vessel, however, at least one electrode or the electrodes of one polarity need to be separated from the interior of the discharge vessel by a dielectric, for example by a dielectric coating. This dielectric barrier results in a so-called dielectrically impeded discharge on one side during operation. Alternatively, all of the inner electrodes may also be provided with a dielectric coating. This is a dielectrically impeded discharge on both sides. The latter relates in particular also to the already mentioned case in which all of the electrodes are arranged outside of the discharge vessel.
Owing to the dielectric barrier between at least one electrode and the discharge medium, a voltage which changes over time, for example a sinusoidal AC voltage, is required for operating a dielectric barrier discharge lamp. The pulsed operation documented in U.S. Pat. No. 5,604,410 has proven to be particularly efficient.
The document U.S. Pat. No. 6,323,600 has disclosed a circuit arrangement for operating a dielectric barrier discharge lamp in accordance with the abovementioned pulsed operation. For this purpose, pulse voltage sequences of a few kilovolts (kV) and pulse repetition frequencies of typically from 25 to 80 kHz are produced with the aid of a flyback converter.
One disadvantage is the fact that conventional high-voltage cables—these are generally individual cables—have high losses owing to their relatively high capacitance at high frequencies. Since the capacitance of a dielectric barrier discharge lamp is lower than the capacitance of long, conventional high-voltage cables, the actual power injected into the connected lamp is thus reduced. These effects are particularly important during the pulsed operation mentioned above, since the pulse voltages have other higher-frequency components in addition to the pulse repetition frequency of typically from 50 to 200 kHz. In particular in the case of relatively long high-voltage cables, the power losses can even result in the lamp no longer being ignited. Therefore, until now only relatively short connection cables have been used, typically of approximately from 25 to 35 cm in length.